The present application relates generally to wind turbines and, more particularly, to a method and apparatus for measuring wind velocity.
Wind turbines typically include a plurality of blades that are used to convert kinetic energy from oncoming wind to mechanical energy for use in producing electrical power. To optimize operation of wind turbines, it is often useful or necessary to determine a velocity of oncoming wind.
Accordingly, at least some known wind turbines are equipped with cup-based or cup anemometers that measure wind velocity and a direction of the wind. Known anemometers use a plurality of devices, such as hollow hemispheres, that are rotatably coupled about a vertical rod. When exposed to wind, the plurality of devices rotate about the rod and an electrical device determines the rotational speed of the devices and calculates the wind velocity. The anemometer may also be used in conjunction with a separate vane that determines the wind direction. Accordingly, because such cup anemometers use rotating components, they may be susceptible to mechanical failure. Moreover, because such components must be exposed to the elements to work effectively, such anemometers may be vulnerable to freezing. Furthermore, cup anemometers must be physically taken to a wind tunnel for calibration.
Other known wind turbines may use ultrasonic anemometers to measure wind velocity and direction. Known ultrasonic anemometers use a plurality of transducers that send out ultrasonic pulses from different directions. When exposed to wind, ultrasonic pulses traveling against wind flow are slowed, and ultrasonic pulses traveling with wind flow are accelerated. An electrical device determines a difference in transit time for the pulses sent in different directions, and calculates wind velocity and direction. A disadvantage to using ultrasonic anemometers is that they are expensive. Moreover, ultrasonic anemometers may be adversely affected by other gases or particles contained in wind flow.